Oil Spill Risk and Ecological Impact Assessment

Simon Mustoe, BSc (Hons), CEnvP, MEIANZ, MIEEM

Incidents like the Pacific Adventurer oil spill off Queensland's Sunshine Coast could raise questions about ecological assessment methods relating to these high risk, low likelihood scenarios, where consequence is difficult or impossible to quantify.

Location of Queensland's recent oil spill

Any precautionary assessment of likely ecological impacts from substantial oil and chemical spills should always find them to be low likelihood, severe consequence scenarios. In conventional risk matrices, this means a 'high risk'. Although the overall risk can be crudely modelled and response measures prepared, there is no saying exactly when or where any impact will occur, and therefore how ecologically significant it may be. The consequence of oil and chemical spills varies from negligible or generally severe in the case of large spills, to negligible or locally severe in the case of small spills.

The ecological "significance" of an impact is unpredictable because spill size and geographic area are only confounding variables - it is more a matter of whether specific environmental factors at the time, (weather, tides, sea state etc) cause the spill to move into areas where there are valuable ecological / social assets. There are many cases of large spills that have missed important assets but other small spills that have had significant effect. For example, in December 1999 the Erika spilt 12-15,000 tonnes of heavy fuel oil into the bay of Biscay and because it happened in winter, it was likely to have killed 5% of Europe's breeding Northern Guillemots. The Amoco Cadiz in March 1978 spilt twenty times more oil but only a tenth of the number of birds were affected, compared to the Erika (Mustoe, 1999).

The AMOCO CADIZ ran aground off the coast of Brittany, France on March 16, 1978, spilling 68.7 million gallons of oil. It is currently number 6 on the list of the largest oil spills of all time but had a relatively small impact on seabirds.

Because we cannot precisely predict or pre-empt the true 'consequence' of any spill, we have to accept to some extent, that it may be severe and depend on managing after-effects. As shown in the recent Queensland spill, a well resourced and prepared authority can do this quite quickly and successfully. But should the emphasis be placed so heavily on the tax payer and those who administrate policies like Australia and New Zealand's National Marine Oil Spill Contingency Plans? ("The National Plans", AMSA, 2005 & MNZ, 2008). Are we, as professionals, under-selling the need for information and risk management at the EIA stage?

The fact is that EIAs cannot easily recommend significant investment in environmental management when the probability of a serious spill event is very low and each operator is part of a large network of vessels with overall cumulative risk. Consequently, rigorous assessment of oil and chemical spill risk tends to take a back seat in the EIA process. It is rarely considered beyond the intent to follow existing and established rules, especially those of the International Maritime Organisation and National Plans. However, these plans depend on specific ecological information in order to be effective.

An example of a vulnerability map for marine fauna in Port Phillip Bay in winter. Areas are broadly defined as high, medium or low, depending on the density of species with different sensitivity to surface pollutants. This information, along with a host of other data, helps managers make swift decisions about how to react to spills.

Following environmental assessment for the Channel Deepening Project in Melbourne, the Victorian Government's Marine and Freshwater Resources Institute were first able to integrate at-sea abundance and distribution data for seabirds and marine mammals into the National Oil Spill Response Atlas, part of the National Plan. Before this, the only biodiversity knowledge they had was of the coast. Since the most substantial impacts of oil on seabirds, cetaceans and marine reptiles happens whilst they are at sea, this extra information is critical. Standard approaches to estimating risk combine information about distribution, abundance and behaviour, especially how much time animals spend at or on the surface (Williams et al., 1995). Similar approaches have been used in the Falkland Islands (White et al., 1999) and parts of the Atlantic (Skov et al., 2002).

On the edge of the Southern Ocean, Australia and New Zealand have significant colonies of internationally important seabirds and the offshore environment is as notable as what is onshore. Baseline knowledge about the behaviour and distribution of seabirds at sea however, is not routinely collected, even by the oil industry. This is despite the fact that observers are regularly placed on marine seismic vessels for oil and gas exploration. They collect little more than sporadic whale and dolphin sightings, which is of little consequence for spatial GIS mapping of biodiversity and risk. The many hours between sightings could be spent investing in future management of oil spill risk. There are also fisheries observers, ecotourism operations, bird-watching groups (for 25 years, birders off New Zealand and Australia have chartered vessels to remote marine areas), all of whom collect data that can be readily analysed and used in biodiversity mapping and spatial planning.

If a network of at-sea information was established, it would enable consultants to recommend some investment of time and resources at the EIA stage and contribute to Oil Spill Response Atlases.

Because our economy depends on transportation of oil and chemicals overseas, we have to take some responsibility for spills occurring and this is why the onus cannot be placed entirely on vessel operators. Substantial legal concessions are offered to companies that cause spills but cooperate fully with the authorities. Pre-emptive contribution of data to contingency plans is just another way that corporate cooperation could be demonstrated but it can also reduce the likelihood of an incident. As indicated above, knowledge about the seasonal distribution and abundance of marine fauna, particularly seabirds, can help predict the likelihood of a major incident, potentially leading to avoidance of high risk areas at high risk times, and helping authorities make quick decisions during spills - such as where to focus containment equipment or dispersants.

Placing more expectation on the operator at the EIA stage means more substantial binding conditions and better corporate awareness of the need to manage their environmental performance and that of their contracted vessels at sea. If the recent incident had occurred in December, the beach-nesting habitat of Loggerhead Turtles could have been seriously affected.

A Loggerhead Turtle at sea off the Australian coast

Only a few hundred Loggerheads remain the east coast and they protected as Marine, Migratory and Endangered species under the Environment Protection and Biodiversity Conservation Act 1999 (Cth) ("EPBC Act"). Little or no mention has been made of the possibility that a significant proportion of animals could have died at sea. Perhaps effort is needed to determine if this is the case? Ironically, the EPBC Act controls impacts out to 200Nm or further but the authorities mostly concerned with clean-up are constrained by data from above the high water mark or at the most, within a few kilometres of the coast. The oil spill risk map for the Great Barrier Reef is notably coastal. It does not include much of the offshore areas of the southern reef, such as the Swaines, even though there are a number of shipping routes.

If this spill had moved offshore and not hit the Sunshine Coast beaches, would we have been less concerned? Would our lack of concern have reflected an actual reduction in impact? The truth is we would not know. So the question remains whether there is a way to facilitate the collection and dissemination of at-sea biodiversity data so we can make better decisions about marine environmental management? If this can be done, it could help lead to a reduction in the likelihood and consequence of oil spills and reduce the risk to corporations that undertake these risky operations on our behalf.

Simon Mustoe is a Certified Environmental Practitioner, Director of AES Applied Ecology Solutions and specialises in marine biodiversity assessment, especially on marine vertebrates including cetaceans, seabirds and marine turtles.


AMSA (2005) National Marine Oil Spill Contingency Plan: AustraliaŹ¼s “National Plan to Combat Pollution of the Sea by Oil and Other Noxious and Hazardous Substances”. Australian Marine Safety Authority, Canberra. Available online at http://www.amsa.gov.au/marine_environment_protection/National_Plan/Contingency_Plans_and_Management/Oil_Spill_Contingency_Plan.asp
MNZ (2008) National Marine Oil Spill Contingency Plan, Maritime New Zealand. Available on line at http://www.mnz.govt.nz/publications/pollution_response/NationalPlan.pdf
Mustoe, S. (1999) The Erika Oil Spill. In Cresswell, G and Walker, D. (eds) A Report on the Whales, Dolphins and Seabirds of the Bay of Biscay and English Channel. Orca No 1. Pp 96-100.
Skov, H., Upton, A.J., Reid, J.B., Webb, A., Samuel, J.T., & Durinck, J. (2002). Dispersion and vulnerability of marine birds and cetaceans in Faroese waters. Joint Nature Conservation Committee, Peterborough
White, R.W., Reid, J.B., Black, A.D. & Gillon, K.W. (1999). Seabird and marine mammal dispersion in the waters around the Falkland Islands 1998-1999. In. Joint Nature Conservation Committee, Aberdeen.
Williams, J.M., Tasker, M.L., Carter, I.C., & Webb, A. (1995) A method of assessing seabird vulnerability to surface pollutants. Ibis, 137

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